26 results on '"Offringa, A.R."'
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2. Transient RFI environment of LOFAR-LBA at 72-75 MHz. Impact on ultra-widefield AARTFAAC Cosmic Explorer observations of the redshifted 21-cm signal
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Gehlot, B.K., primary, Koopmans, L.V.E., additional, Brackenhoff, S.A., additional, Ceccotti, E., additional, Ghosh, S., additional, Hofer, C., additional, Mertens, F.G., additional, Mevius, M., additional, Munshi, S., additional, Offringa, A.R., additional, Pandey, V.N., additional, Rowlinson, A., additional, Shulevski, A., additional, Wijers, R.A.M.J., additional, Yatawatta, S., additional, and Zaroubi, S., additional
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- 2023
- Full Text
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3. Improved upper limits on the 21-cm signal power spectrum of neutral hydrogen at $\boldsymbol{z \approx 9.1}$ from LOFAR
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Mertens, F.G., Mevius, M., Koopmans, L.V.E, Offringa, A.R., Mellema, G., Zaroubi, S., Brentjens, M.A., Gan, H., Gehlot, B.K., Pandey, V.N., Sardarabadi, A.M., Vedantham, H.K., Yatawatta, S., Asad, K.M.B., Ciardi, B., Chapman, E., Gazagnes, S., Ghara, R., Ghosh, A., Giri, S.K., Iliev, I.T., Jelíc, V., Kooistra, R., Mondal, R., Schaye, J., Silva, M.B., Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA (UMR_8112)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY)
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Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,techniques: interferometric ,cosmology: observations ,first stars ,reionization ,FOS: Physical sciences ,dark ages ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,methods: data analysis ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
A new upper limit on the 21-cm signal power spectrum at a redshift of $z \approx 9.1$ is presented, based on 141 hours of data obtained with the Low-Frequency Array (LOFAR). The analysis includes significant improvements in spectrally-smooth gain-calibration, Gaussian Process Regression (GPR) foreground mitigation and optimally-weighted power spectrum inference. Previously seen `excess power' due to spectral structure in the gain solutions has markedly reduced but some excess power still remains with a spectral correlation distinct from thermal noise. This excess has a spectral coherence scale of $0.25 - 0.45$\,MHz and is partially correlated between nights, especially in the foreground wedge region. The correlation is stronger between nights covering similar local sidereal times. A best 2-$\sigma$ upper limit of $\Delta^2_{21} < (73)^2\,\mathrm{mK^2}$ at $k = 0.075\,\mathrm{h\,cMpc^{-1}}$ is found, an improvement by a factor $\approx 8$ in power compared to the previously reported upper limit. The remaining excess power could be due to residual foreground emission from sources or diffuse emission far away from the phase centre, polarization leakage, chromatic calibration errors, ionosphere, or low-level radio-frequency interference. We discuss future improvements to the signal processing chain that can further reduce or even eliminate these causes of excess power., Comment: 27 pages, 14 figues, accepted in MNRAS (updated with reference to accompanying paper)
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- 2020
4. Modelling and peeling extended sources with shapelets: A Fornax A case study
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Line, Jack, Mitchell, D.A., Pindor, B., Riding, J.L., McKinley, Ben, Webster, R.L., Trott, Cathryn, Hurley-Walker, Natasha, Offringa, A.R., Line, Jack, Mitchell, D.A., Pindor, B., Riding, J.L., McKinley, Ben, Webster, R.L., Trott, Cathryn, Hurley-Walker, Natasha, and Offringa, A.R.
- Abstract
To make a power spectrum (PS) detection of the 21-cm signal from the Epoch of Reionisation (EoR), one must avoid/subtract bright foreground sources. Sources such as Fornax A present a modelling challenge due to spatial structures spanning from arc seconds up to a degree. We compare modelling with multi-scale (MS) CLEAN components to 'shapelets', an alternative set of basis functions. We introduce a new image-based shapelet modelling package, SHAMFI. We also introduce a new CUDA simulation code (WODEN) to generate point source, Gaussian, and shapelet components into visibilities. We test performance by modelling a simulation of Fornax A, peeling the model from simulated visibilities, and producing a residual PS. We find the shapelet method consistently subtracts large-angular-scale emission well, even when the angular resolution of the data is changed. We find that when increasing the angular resolution of the data, the MS CLEAN model worsens at large angular scales. When testing on real Murchison Widefield Array data, the expected improvement is not seen in real data because of the other dominating systematics still present. Through further simulation, we find the expected differences to be lower than obtainable through current processing pipelines. We conclude shapelets are worthwhile for subtracting extended galaxies, and may prove essential for an EoR detection in the future, once other systematics have been addressed.
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- 2020
5. Systematic effects in LOFAR data: A unified calibration strategy
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De Gasperin, F., Dijkema, T.J., Drabent, A., Mevius, M., Rafferty, D., Van Weeren, R., Brüggen, M., Callingham, J.R., Emig, K.L., Heald, G., Intema, Huib, Morabito, L.K., Offringa, A.R., Oonk, R., Orrù, E., Röttgering, H., Sabater, J., Shimwell, T., Shulevski, A., Williams, W., De Gasperin, F., Dijkema, T.J., Drabent, A., Mevius, M., Rafferty, D., Van Weeren, R., Brüggen, M., Callingham, J.R., Emig, K.L., Heald, G., Intema, Huib, Morabito, L.K., Offringa, A.R., Oonk, R., Orrù, E., Röttgering, H., Sabater, J., Shimwell, T., Shulevski, A., and Williams, W.
- Abstract
Context. New generation low-frequency telescopes are exploring a new parameter space in terms of depth and resolution. The data taken with these interferometers, for example with the LOw Frequency ARray (LOFAR), are often calibrated in a low signal-to-noise ratio regime and the removal of critical systematic effects is challenging. The process requires an understanding of their origin and properties. Aim. In this paper we describe the major systematic effects inherent to next generation low-frequency telescopes, such as LOFAR. With this knowledge, we introduce a data processing pipeline that is able to isolate and correct these systematic effects. The pipeline will be used to calibrate calibrator observations as the first step of a full data reduction process. Methods. We processed two LOFAR observations of the calibrator 3C 196: the first using the Low Band Antenna (LBA) system at 42-66 MHz and the second using the High Band Antenna (HBA) system at 115-189 MHz. Results. We were able to isolate and correct for the effects of clock drift, polarisation misalignment, ionospheric delay, Faraday rotation, ionospheric scintillation, beam shape, and bandpass. The designed calibration strategy produced the deepest image to date at 54 MHz. The image has been used to confirm that the spectral energy distribution of the average radio source population tends to flatten at low frequencies. Conclusions. We prove that LOFAR systematic effects can be described by a relatively small number of parameters. Furthermore, the identification of these parameters is fundamental to reducing the degrees of freedom when the calibration is carried out on fields that are not dominated by a strong calibrator.
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- 2019
6. The Challenges of Low-Frequency Radio Polarimetry: Lessons from the Murchison Widefield Array
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Lenc, E., Anderson, C.S, Barry, N., Bowman, J.D., Cairns, I.H., Farnes, J.S., Gaensler, B.M., Heald, G., Johnston-Hollitt, M., Kaplan, D.L., Lynch, C.R., McCauley, P.I., Mitchell, D.A., Morgan, J., Morales, M.F., Murphy, T., Offringa, A.R., Ord, S.M., Pindor, B., Riseley, C., Sadler, E.M., Sobey, C, Sokolowski, M., Sullivan, I.S., O’Sullivan, S.P., Sun, X.H., Tremblay, S.E., Trott, C.M., Wayth, R.B., Lenc, E., Anderson, C.S, Barry, N., Bowman, J.D., Cairns, I.H., Farnes, J.S., Gaensler, B.M., Heald, G., Johnston-Hollitt, M., Kaplan, D.L., Lynch, C.R., McCauley, P.I., Mitchell, D.A., Morgan, J., Morales, M.F., Murphy, T., Offringa, A.R., Ord, S.M., Pindor, B., Riseley, C., Sadler, E.M., Sobey, C, Sokolowski, M., Sullivan, I.S., O’Sullivan, S.P., Sun, X.H., Tremblay, S.E., Trott, C.M., and Wayth, R.B.
- Abstract
Contains fulltext : 178478.pdf (publisher's version ) (Closed access) Contains fulltext : 178478.pdf (preprint version ) (Open Access)
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- 2017
7. Linear polarization structures in LOFAR observations of the interstellar medium in the 3C 196 field
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Jelic, V., Bruyn, A.G. de, Pandey, V.N., Mevius, M., Haverkorn, M., Brentjens, M.A., Koopmans, L.V.E., Zaroubi, S., Abdalla, F.B., Asad, K.M.B., Bus, S., Chapman, E., Ciardi, B., Fernandez, E.R., Ghosh, A., Harker, G., Iliev, I.T., Jensen, H., Kazemi, S., Mellema, G., Offringa, A.R., Patil, A.H., Vedantham, H.K., Yatawatta, S., Jelic, V., Bruyn, A.G. de, Pandey, V.N., Mevius, M., Haverkorn, M., Brentjens, M.A., Koopmans, L.V.E., Zaroubi, S., Abdalla, F.B., Asad, K.M.B., Bus, S., Chapman, E., Ciardi, B., Fernandez, E.R., Ghosh, A., Harker, G., Iliev, I.T., Jensen, H., Kazemi, S., Mellema, G., Offringa, A.R., Patil, A.H., Vedantham, H.K., and Yatawatta, S.
- Abstract
Contains fulltext : 150877.pdf (postprint version ) (Open Access)
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- 2015
8. First LOFAR results on galaxy clusters
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Ferrari, C., van Bemmel, I., Bonafede, A., Bîrzan, L., Brüggen, M., Brunetti, G., Cassano, R., Conway, J., De Gasperin, F., Heald, G., Jackson, N., Macario, G., McKean, J., Offringa, A.R., Orrù, E., Pizzo, R., Rafferty, D.A., Röttgering, H.J.A., Shulevski, A., Tasse, C., van der Tol, S., van Weeren, R.J., Wise, M., van Zwieten, J.E., LOFAR Collaboration, [Unknown], Boissier, S., de Laverny, P., Nardetto, N., Samadi, R., Valls-Gabaud, D., Wozniak, H., and High Energy Astrophys. & Astropart. Phys (API, FNWI)
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Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
Deep radio observations of galaxy clusters have revealed the existence of diffuse radio sources related to the presence of relativistic electrons and weak magnetic fields in the intracluster volume. The role played by this non-thermal intracluster component on the thermodynamical evolution of galaxy clusters is debated, with important implications for cosmological and astrophysical studies of the largest gravitationally bound structures of the Universe. The low surface brightness and steep spectra of diffuse cluster radio sources make them more easily detectable at low-frequencies. LOFAR is the first instrument able to detect diffuse radio emission in hundreds of massive galaxy clusters up to their formation epoch (z ˜ 1). We present the first observations of clusters imaged by LOFAR and the huge perspectives opened by this instrument for non-thermal cluster studies.
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- 2012
9. A LOFAR RFI detection pipeline and its first results
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Offringa, A.R., Bruyn, A.G. de, Zaroubi, S., Biehl, M., Groningen, University of, Intelligente Systemen, and Sterrenkunde
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- 2010
10. Initial deep LOFAR observations of epoch of reionization windows I. The north celestial pole
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Yatawatta, S., Bruyn, A.G. de, Brentjens, M.A., Labropoulos, P., Pandey, V.N., Kazemi, S., Zaroubi, S., Koopmans, L.V.E., Offringa, A.R., Jelic, V., Martinez, O., Falcke, H., Fallows, R.A., Orru, E., Veen, S. ter, Zarka, P., Yatawatta, S., Bruyn, A.G. de, Brentjens, M.A., Labropoulos, P., Pandey, V.N., Kazemi, S., Zaroubi, S., Koopmans, L.V.E., Offringa, A.R., Jelic, V., Martinez, O., Falcke, H., Fallows, R.A., Orru, E., Veen, S. ter, and Zarka, P.
- Abstract
Contains fulltext : 111358.pdf (preprint version ) (Open Access)
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- 2013
11. The brightness and spatial distributions of terrestrial radio sources
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Offringa, A.R., Bruyn, A.G. de, Zaroubi, S., Veen, S. ter, Wucknitz, O., et al., Offringa, A.R., Bruyn, A.G. de, Zaroubi, S., Veen, S. ter, Wucknitz, O., and et al.
- Abstract
Contains fulltext : 117282.pdf (preprint version ) (Open Access)
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- 2013
12. The LOFAR radio environment
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Offringa, A.R., Bruyn, A.G. de, Zaroubi, S., Falcke, H., Wucknitz, O., et al., Offringa, A.R., Bruyn, A.G. de, Zaroubi, S., Falcke, H., Wucknitz, O., and et al.
- Abstract
Contains fulltext : 111267.pdf (preprint version ) (Open Access)
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- 2013
13. Interference detection results with LOFAR.
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Offringa, A.R. and de Bruyn, A.G.
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- 2011
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14. Simulating the 21 cm forest detectable with LOFAR and SKA in the spectra of high-z GRBs
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Ciardi, B., Inoue, S., Abdalla, F.B., Asad, K., Bernardi, G., Bolton, James S., Brentjens, M., de Bruyn, A.G., Chapman, E., Daiboo, S., Fernandez, E.R., Ghosh, A., Graziani, L., Harker, G.J.A., Iliev, I.T., Jelic, V., Jensen, H., Kazemi, S., Koopmans, L.V.E., Martinez, O., Maselli, A., Mellema, G., Offringa, A.R., Pandey, V.N., Schaye, Joop, Thomas, R., Vedantham, H., Yatawatta, S., Zaroubi, S., Ciardi, B., Inoue, S., Abdalla, F.B., Asad, K., Bernardi, G., Bolton, James S., Brentjens, M., de Bruyn, A.G., Chapman, E., Daiboo, S., Fernandez, E.R., Ghosh, A., Graziani, L., Harker, G.J.A., Iliev, I.T., Jelic, V., Jensen, H., Kazemi, S., Koopmans, L.V.E., Martinez, O., Maselli, A., Mellema, G., Offringa, A.R., Pandey, V.N., Schaye, Joop, Thomas, R., Vedantham, H., Yatawatta, S., and Zaroubi, S.
- Abstract
We investigate the feasibility of detecting 21 cm absorption features in the afterglow spectra of high redshift long Gamma Ray Bursts (GRBs). This is done employing simulations of cosmic reionization, together with estimates of the GRB radio afterglow flux and the instrumental characteristics of the LOw Frequency ARray (LOFAR). We find that absorption features could be marginally (with a S/N larger than a few) detected by LOFAR at z ≳ 7 if the GRB is a highly energetic event originating from Pop III stars, while the detection would be easier if the noise were reduced by one order of magnitude, i.e. similar to what is expected for the first phase of the Square Kilometre Array (SKA1-low). On the other hand, more standard GRBs are too dim to be detected even with ten times the sensitivity of SKA1-low, and only in the most optimistic case can a S/N larger than a few be reached at z ≳ 9.
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15. Simulating the 21 cm forest detectable with LOFAR and SKA in the spectra of high-z GRBs
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Ciardi, B., Inoue, S., Abdalla, F.B., Asad, K., Bernardi, G., Bolton, James S., Brentjens, M., de Bruyn, A.G., Chapman, E., Daiboo, S., Fernandez, E.R., Ghosh, A., Graziani, L., Harker, G.J.A., Iliev, I.T., Jelic, V., Jensen, H., Kazemi, S., Koopmans, L.V.E., Martinez, O., Maselli, A., Mellema, G., Offringa, A.R., Pandey, V.N., Schaye, Joop, Thomas, R., Vedantham, H., Yatawatta, S., Zaroubi, S., Ciardi, B., Inoue, S., Abdalla, F.B., Asad, K., Bernardi, G., Bolton, James S., Brentjens, M., de Bruyn, A.G., Chapman, E., Daiboo, S., Fernandez, E.R., Ghosh, A., Graziani, L., Harker, G.J.A., Iliev, I.T., Jelic, V., Jensen, H., Kazemi, S., Koopmans, L.V.E., Martinez, O., Maselli, A., Mellema, G., Offringa, A.R., Pandey, V.N., Schaye, Joop, Thomas, R., Vedantham, H., Yatawatta, S., and Zaroubi, S.
- Abstract
We investigate the feasibility of detecting 21 cm absorption features in the afterglow spectra of high redshift long Gamma Ray Bursts (GRBs). This is done employing simulations of cosmic reionization, together with estimates of the GRB radio afterglow flux and the instrumental characteristics of the LOw Frequency ARray (LOFAR). We find that absorption features could be marginally (with a S/N larger than a few) detected by LOFAR at z ≳ 7 if the GRB is a highly energetic event originating from Pop III stars, while the detection would be easier if the noise were reduced by one order of magnitude, i.e. similar to what is expected for the first phase of the Square Kilometre Array (SKA1-low). On the other hand, more standard GRBs are too dim to be detected even with ten times the sensitivity of SKA1-low, and only in the most optimistic case can a S/N larger than a few be reached at z ≳ 9.
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16. Simulating the 21 cm forest detectable with LOFAR and SKA in the spectra of high-z GRBs
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Ciardi, B., Inoue, S., Abdalla, F.B., Asad, K., Bernardi, G., Bolton, James S., Brentjens, M., de Bruyn, A.G., Chapman, E., Daiboo, S., Fernandez, E.R., Ghosh, A., Graziani, L., Harker, G.J.A., Iliev, I.T., Jelic, V., Jensen, H., Kazemi, S., Koopmans, L.V.E., Martinez, O., Maselli, A., Mellema, G., Offringa, A.R., Pandey, V.N., Schaye, Joop, Thomas, R., Vedantham, H., Yatawatta, S., Zaroubi, S., Ciardi, B., Inoue, S., Abdalla, F.B., Asad, K., Bernardi, G., Bolton, James S., Brentjens, M., de Bruyn, A.G., Chapman, E., Daiboo, S., Fernandez, E.R., Ghosh, A., Graziani, L., Harker, G.J.A., Iliev, I.T., Jelic, V., Jensen, H., Kazemi, S., Koopmans, L.V.E., Martinez, O., Maselli, A., Mellema, G., Offringa, A.R., Pandey, V.N., Schaye, Joop, Thomas, R., Vedantham, H., Yatawatta, S., and Zaroubi, S.
- Abstract
We investigate the feasibility of detecting 21 cm absorption features in the afterglow spectra of high redshift long Gamma Ray Bursts (GRBs). This is done employing simulations of cosmic reionization, together with estimates of the GRB radio afterglow flux and the instrumental characteristics of the LOw Frequency ARray (LOFAR). We find that absorption features could be marginally (with a S/N larger than a few) detected by LOFAR at z ≳ 7 if the GRB is a highly energetic event originating from Pop III stars, while the detection would be easier if the noise were reduced by one order of magnitude, i.e. similar to what is expected for the first phase of the Square Kilometre Array (SKA1-low). On the other hand, more standard GRBs are too dim to be detected even with ten times the sensitivity of SKA1-low, and only in the most optimistic case can a S/N larger than a few be reached at z ≳ 9.
- Full Text
- View/download PDF
17. Simulating the 21 cm forest detectable with LOFAR and SKA in the spectra of high-z GRBs
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Ciardi, B., Inoue, S., Abdalla, F.B., Asad, K., Bernardi, G., Bolton, James S., Brentjens, M., de Bruyn, A.G., Chapman, E., Daiboo, S., Fernandez, E.R., Ghosh, A., Graziani, L., Harker, G.J.A., Iliev, I.T., Jelic, V., Jensen, H., Kazemi, S., Koopmans, L.V.E., Martinez, O., Maselli, A., Mellema, G., Offringa, A.R., Pandey, V.N., Schaye, Joop, Thomas, R., Vedantham, H., Yatawatta, S., Zaroubi, S., Ciardi, B., Inoue, S., Abdalla, F.B., Asad, K., Bernardi, G., Bolton, James S., Brentjens, M., de Bruyn, A.G., Chapman, E., Daiboo, S., Fernandez, E.R., Ghosh, A., Graziani, L., Harker, G.J.A., Iliev, I.T., Jelic, V., Jensen, H., Kazemi, S., Koopmans, L.V.E., Martinez, O., Maselli, A., Mellema, G., Offringa, A.R., Pandey, V.N., Schaye, Joop, Thomas, R., Vedantham, H., Yatawatta, S., and Zaroubi, S.
- Abstract
We investigate the feasibility of detecting 21 cm absorption features in the afterglow spectra of high redshift long Gamma Ray Bursts (GRBs). This is done employing simulations of cosmic reionization, together with estimates of the GRB radio afterglow flux and the instrumental characteristics of the LOw Frequency ARray (LOFAR). We find that absorption features could be marginally (with a S/N larger than a few) detected by LOFAR at z ≳ 7 if the GRB is a highly energetic event originating from Pop III stars, while the detection would be easier if the noise were reduced by one order of magnitude, i.e. similar to what is expected for the first phase of the Square Kilometre Array (SKA1-low). On the other hand, more standard GRBs are too dim to be detected even with ten times the sensitivity of SKA1-low, and only in the most optimistic case can a S/N larger than a few be reached at z ≳ 9.
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- View/download PDF
18. Cassiopeia A, Cygnus A, Taurus A, and Virgo A at ultra-low radio frequencies
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F. de Gasperin, J. Vink, J. P. McKean, A. Asgekar, I. Avruch, M. J. Bentum, R. Blaauw, A. Bonafede, J. W. Broderick, M. Brüggen, F. Breitling, W. N. Brouw, H. R. Butcher, B. Ciardi, V. Cuciti, M. de Vos, S. Duscha, J. Eislöffel, D. Engels, R. A. Fallows, T. M. O. Franzen, M. A. Garrett, A. W. Gunst, J. Hörandel, G. Heald, M. Hoeft, M. Iacobelli, L. V. E. Koopmans, A. Krankowski, P. Maat, G. Mann, M. Mevius, G. Miley, R. Morganti, A. Nelles, M. J. Norden, A. R. Offringa, E. Orrú, H. Paas, V. N. Pandey, M. Pandey-Pommier, R. Pekal, R. Pizzo, W. Reich, A. Rowlinson, H. J. A. Rottgering, D. J. Schwarz, A. Shulevski, O. Smirnov, C. Sobey, M. Soida, M. Steinmetz, M. Tagger, M. C. Toribio, A. van Ardenne, A. J. van der Horst, M. P. van Haarlem, R. J. van Weeren, C. Vocks, O. Wucknitz, P. Zarka, P. Zucca, Astronomy, Kapteyn Astronomical Institute, Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), De Gasperin F., Vink J., McKean J.P., Asgekar A., Avruch I., Bentum M.J., Blaauw R., Bonafede A., Broderick J.W., Bruggen M., Breitling F., Brouw W.N., Butcher H.R., Ciardi B., Cuciti V., De Vos M., Duscha S., Eisloffel J., Engels D., Fallows R.A., Franzen T.M.O., Garrett M.A., Gunst A.W., Horandel J., Heald G., Hoeft M., Iacobelli M., Koopmans L.V.E., Krankowski A., Maat P., Mann G., Mevius M., Miley G., Morganti R., Nelles A., Norden M.J., Offringa A.R., Orru E., Paas H., Pandey V.N., Pandey-Pommier M., Pekal R., Pizzo R., Reich W., Rowlinson A., Rottgering H.J.A., Schwarz D.J., Shulevski A., Smirnov O., Sobey C., Soida M., Steinmetz M., Tagger M., Toribio M.C., Van Ardenne A., Van Der Horst A.J., Van Haarlem M.P., Van Weeren R.J., Vocks C., Wucknitz O., Zarka P., Zucca P., High Energy Astrophys. & Astropart. Phys (API, FNWI), Gravitation and Astroparticle Physics Amsterdam, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES)
- Subjects
Astronomy ,media_common.quotation_subject ,Astrophysics::High Energy Astrophysical Phenomena ,radio continuum: general ,FOS: Physical sciences ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,radio continuum ,law.invention ,Telescope ,law ,0103 physical sciences ,Angular resolution ,[PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det] ,Surface brightness ,010306 general physics ,Cygnus A ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,media_common ,High Energy Astrophysical Phenomena (astro-ph.HE) ,[PHYS]Physics [physics] ,Physics ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy and Astrophysics ,LOFAR ,Astrophysics - Astrophysics of Galaxies ,interferometric [techniques] ,Cassiopeia A ,techniques: interferometric ,13. Climate action ,Space and Planetary Science ,Sky ,general ,Astrophysics of Galaxies (astro-ph.GA) ,interferometric ,ddc:520 ,general [radio continuum] ,Radio frequency ,Astrophysics - High Energy Astrophysical Phenomena ,Astrophysics - Instrumentation and Methods for Astrophysics ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,techniques ,general [ontinuum] - Abstract
The four persistent radio sources in the northern sky with the highest flux density at metre wavelengths are Cassiopeia A, Cygnus A, Taurus A, and Virgo A; collectively they are called the A-team. Their flux densities at ultra-low frequencies (, 7 pages, 2 figures, accepted A&A, online data on A&A website
- Published
- 2020
19. Lunar occultation of the diffuse radio sky: LOFAR measurements between 35 and 80 MHz
- Author
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Vibor Jelić, Martin Bell, Gottfried Mann, Michael W. Wise, Gianni Bernardi, Wilfred Frieswijk, Jörg R. Hörandel, Garrelt Mellema, J. W. Broderick, J. Anderson, E. de Geus, George Heald, Y. Tang, K. M. B. Asad, M. J. Norden, Heino Falcke, Michiel A. Brentjens, Luitje Koopmans, V. I. Kondratiev, Arthur Corstanje, de Antonius Bruyn, A. Renting, Michel Tagger, Ben Stappers, Elizabeth Fernandez, F. de Gasperin, S. Kazemi, Emanuela Orrú, O. Martinez-Rubi, Rob Fender, A. Nelles, Oleg Smirnov, Stefan J. Wijnholds, P. Lambropoulos, A. R. Offringa, Annalisa Bonafede, Emma Chapman, Hannes Jensen, E. Juette, D. Engels, Sera Markoff, C. Toribio, Abhik Ghosh, F. B. Abdalla, Rebecca McFadden, Roberto Pizzo, Marco Iacobelli, Sarod Yatawatta, S. Daiboo, Satyendra Thoudam, W. Reich, D. McKay-Bukowski, Dominik J. Schwarz, D. D. Mulcahy, A. H. Patil, Frank Breitling, Jochen Eislöffel, B. Ciardi, Maaijke Mevius, Mark J. Bentum, C. Tasse, V. Veligatla, A. G. Polatidis, Matthias Steinmetz, S. Bus, Vishambhar Pandey, M. Kuniyoshi, Philippe Zarka, S. ter Veen, Adam Deller, Chiara Ferrari, A. W. Gunst, Ashish Asgekar, Matthias Hoeft, Philip Best, A. Shulevski, John D. Swinbank, H. Munk, Marcus Brüggen, Geraint Harker, Jean-Mathias Grießmeier, Tim Hassall, Christian Vocks, Saleem Zaroubi, Rajat M. Thomas, John McKean, Harvey Butcher, M. Pandey-Pommier, S. Duscha, Harish Vedantham, Richard Fallows, M. A. Garrett, H. J. A. Röttgering, Olaf Wucknitz, G. Kuper, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], UMR Peuplement Végétaux et Bioagresseurs en Milieu Tropical (UMR PVBMT - INRA), Institut National de la Recherche Agronomique (INRA), Netherlands Institute for Radio Astronomy (ASTRON), University College of London [London] (UCL), Laboratoire de Mécanique des Contacts et des Structures [Villeurbanne] (LaMCoS), Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Mécanique multiphysique pour les matériaux et les procédés (MULTIMAP), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Howard Hugues Medical Institute, Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Departamento de Geologıa, Universidad de Santiago de Chile [Santiago] (USACH), Advanced Computing and Microelectronics Unit [Kolkata] (ACMU), Indian Statistical Institute [Kolkata], Department of Physics and Astronomy [UCL London], Stockholm University, Department of process and energy, Delft University of Technology (TU Delft), Department of Physics, University of Crete [Heraklion] (UOC), Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas (FORTH), Stockholm Observatory Department of Astronomy, Department of Physics and Astronomy [Ghent], Ghent University [Belgium] (UGENT), Spatial Ecology and Epidemiology Group, University of Oxford [Oxford], Plant Ind, Hort Unit, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Institute for Mathematics Applied to Geoscience, National Center for Atmospheric Research [Boulder] (NCAR), CSIRO Astronomy and Space Science, University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), University of Southampton, Radboud university [Nijmegen], Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Metacohorts Consortium, Thüringer Landessternwarte Tautenburg (TLS), Département de Géologie, Université de Montréal [Montréal], Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Unité Scientifique de la Station de Nançay (USN), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Ruhr-Universität Bochum [Bochum], Max-Planck-Institut für Radioastronomie (MPIFR), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), University of Oulu, Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Centre de Recherche Astrophysique de Lyon (CRAL), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Department of Astrophysics [Nijmegen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen]-Radboud university [Nijmegen], Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), European Project: 258942,EC:FP7:ERC,ERC-2010-StG_20091028,FIRSTLIGHT(2010), Howard Hughes Medical Institute (HHMI), Universiteit Gent = Ghent University (UGENT), University of Oxford, Radboud University [Nijmegen], Université de Montréal (UdeM), Universiteit Leiden, Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Grahamstown, Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Radboud University [Nijmegen]-Radboud University [Nijmegen], Agence Nationale de la Recherche (ANR-09-JCJC-0001-01), Peuplements végétaux et bioagresseurs en milieu tropical (UMR PVBMT), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Université de La Réunion (UR), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Pierre et Marie Curie - Paris 6 (UPMC), Universiteit Gent = Ghent University [Belgium] (UGENT), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Vedantham, H.K., Koopmans, L.V.E., de Bruyn, A.G., Wijnholds, S.J., Brentjens, M., Abdalla, F.B., Asad, K.M.B., Bernardi, G., Bus, S., Chapman, E., Ciardi, B., Daiboo, S., Fernandez, E.R., Ghosh, A., Harker, G., Jelic, V., Jensen, H., Kazemi, S., Lambropoulos, P., Martinez-Rubi, O., Mellema, G., Mevius, M., Offringa, A.R., Pandey, V.N., Patil, A.H., Thomas, R.M., Veligatla, V., Yatawatta, S., Zaroubi, S., Anderson, J., Asgekar, A., Bell, M.E., Bentum, M.J., Best, P., Bonafede, A., Breitling, F., Broderick, J., Brüggen, M., Butcher, H.R., Corstanje, A., De Gasperin, F., De Geus, E., Deller, A., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hassall, T.E., Heald, G., Hoeft, M., Hörandel, J., Iacobelli, M., Juette, E., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., McKean, J.P., Mulcahy, D.D., Munk, H., Nelles, A., Norden, M.J., Orru, E., Pandey-Pommier, M., Pizzo, R., Polatidis, A.G., Reich, W., Renting, A., Röttgering, H., Schwarz, D., Shulevski, A., Smirnov, O., Stappers, B.W., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Ter Veen, S., Thoudam, S., Toribio, C., Vocks, C., Wise, M.W., Wucknitz, O., Zarka, P., Astronomy, Kapteyn Astronomical Institute, ITA, GBR, FRA, DEU, NLD, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
- Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,media_common.quotation_subject ,Astrophysics::High Energy Astrophysical Phenomena ,Astronomy ,first stars ,observational [methods] ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,methods: observational ,techniques: interferometric ,Moon ,dark ages ,reionization ,methods: observational – techniques: interferometric – Moon – cosmology: dark ages ,Occultation ,IR-98655 ,Reionization ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,media_common ,EWI-26150 ,Astroparticle physics ,Physics ,Epoch (reference date) ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy and Astrophysics ,LOFAR ,Astronomy and Astrophysic ,Universe ,interferometric [techniques] ,Dark ages, reionization, first star ,Sky ,Space and Planetary Science ,[SDU]Sciences of the Universe [physics] ,Physics::Space Physics ,ComputingMethodologies_DOCUMENTANDTEXTPROCESSING ,Dark Ages ,Astrophysics::Earth and Planetary Astrophysics ,METIS-314921 ,Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
We present radio observations of the Moon between $35$ and $80$ MHz to demonstrate a novel technique of interferometrically measuring large-scale diffuse emission extending far beyond the primary beam (global signal) for the first time. In particular, we show that (i) the Moon appears as a negative-flux source at frequencies $35z>12$) and the Epoch of Reionization ($12>z>5$)., Comment: 15 pages, 11 figures, 1 table
- Published
- 2015
20. Initial LOFAR observations of epoch of reionization windows. II. Diffuse polarized emission in the ELAIS-N1 field
- Author
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F. de Gasperin, A. Horneffer, Jochen Eislöffel, M. A. Garrett, Geraint Harker, Michael Kramer, A. Nelles, J. van Leeuwen, Maaijke Mevius, Wilfred Frieswijk, Y. Tang, Anna M. M. Scaife, S. ter Veen, J. P. Hamaker, V. Veligatla, Marijke Haverkorn, G. Mann, A. W. Gunst, Chiara Ferrari, Rob Fender, D. Engels, Philip Best, Harish Vedantham, A. R. Offringa, John Conway, M. Iacobelli, M. Serylak, E. Juette, Hannes Jensen, James M. Anderson, C. Vocks, Annalisa Bonafede, Heino Falcke, Vibor Jelić, R. J. Dettmar, John McKean, Matthias Hoeft, A. H. Patil, J. W. Broderick, Saleem Zaroubi, P. Maat, Tim Hassall, Harvey Butcher, Aris Karastergiou, H. J. A. Röttgering, Rajat M. Thomas, M. J. Norden, V. I. Kondratiev, Olaf Wucknitz, M. Pandey-Pommier, H. Paas, Gianni Bernardi, Jörg R. Hörandel, Mark J. Bentum, Antonia Rowlinson, Michel Tagger, Garrelt Mellema, H. Munk, C. Tasse, O. Martinez-Rubi, W. Reich, J. D. Bregman, S. Kazemi, Abhik Ghosh, George Heald, Oleg Smirnov, Elizabeth Fernandez, S. Duscha, Dominik J. Schwarz, A. G. Polatidis, I. M. Avruch, Michiel A. Brentjens, W. N. Brouw, Roberto Pizzo, P. Labropoulos, Marcus Brüggen, Ralph A. M. J. Wijers, G. Pietka, Gerard H. Kuper, K. M. B. Asad, Martin Bell, Satyendra Thoudam, Jean-Mathias Griessmeier, Richard Fallows, A. Alexov, Emma Chapman, Ron Beck, A. G. de Bruyn, Luitje Koopmans, Vishambhar Pandey, Adam Deller, C. Toribio, F. B. Abdalla, P. Zarka, Matthias Steinmetz, F. Breitling, B. Ciardi, Jason W. T. Hessels, S. Bus, M. Kuniyoshi, R. Vermeulen, Stefan J. Wijnholds, E. de Geus, Sarod Yatawatta, S. Daiboo, Adam Stewart, A. J. van der Horst, R. J. van Weeren, D. McKay-Bukowski, Netherlands Institute for Radio Astronomy (ASTRON), University College of London [London] (UCL), Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE (UMR_7585)), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, University of Pennsylvania [Philadelphia], SRON Netherlands Institute for Space Research (SRON), Max-Planck-Institut für Radioastronomie (MPIFR), University of Southampton, University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Thüringer Landessternwarte Tautenburg (TLS), Radboud university [Nijmegen], Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics (JBCA), University of Manchester [Manchester], University of Amsterdam [Amsterdam] (UvA), Ruhr-Universität Bochum [Bochum], Vrije Universiteit Medical Centre (VUMC), Vrije Universiteit Amsterdam [Amsterdam] (VU), University of Oulu, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), School of Physics and Astronomy [Southampton], Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), ANR-09-JCJC-0001,OPALES(2009), Jelić, V., De Bruyn, A.G., Mevius, M., Abdalla, F.B., Asad, K.M.B., Bernardi, G., Brentjens, M.A., Bus, S., Chapman, E., Ciardi, B., Daiboo, S., Fernandez, E.R., Ghosh, A., Harker, G., Jensen, H., Kazemi, S., Koopmans, L.V.E., Labropoulos, P., Martinez-Rubi, O., Mellema, G., Offringa, A.R., Pandey, V.N., Patil, A.H., Thomas, R.M., Vedantham, H.K., Veligatla, V., Yatawatta, S., Zaroubi, S., Alexov, A., Anderson, J., Avruch, I.M., Beck, R., Bell, M.E., Bentum, M.J., Best, P., Bonafede, A., Bregman, J., Breitling, F., Broderick, J., Brouw, W.N., Brüggen, M., Butcher, H.R., Conway, J.E., De Gasperin, F., De Geus, E., Deller, A., Dettmar, R.-J., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hamaker, J.P., Hassall, T.E., Haverkorn, M., Heald, G., Hessels, J.W.T., Hoeft, M., Hörandel, J., Horneffer, A., Van Der Horst, A., Iacobelli, M., Juette, E., Karastergiou, A., Kondratiev, V.I., Kramer, M., Kuniyoshi, M., Kuper, G., Van Leeuwen, J., Maat, P., Mann, G., McKay-Bukowski, D., McKean, J.P., Munk, H., Nelles, A., Norden, M.J., Paas, H., Pandey-Pommier, M., Pietka, G., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Rowlinson, A., Scaife, A.M.M., Schwarz, D., Serylak, M., Smirnov, O., Steinmetz, M., Stewart, A., Tagger, M., Tang, Y., Tasse, C., Ter Veen, S., Thoudam, S., Toribio, C., Vermeulen, R., Vocks, C., Van Weeren, R.J., Wijers, R.A.M.J., Wijnholds, S.J., Wucknitz, O., Zarka, P., Astronomy, Kapteyn Astronomical Institute, University of Pennsylvania, Radboud University [Nijmegen], Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), High Energy Astrophys. & Astropart. Phys (API, FNWI), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, Observatoire de Paris - Site de Paris (OP), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and ANR-09-JCJC-0001,OPALES,nOn-thermal Processes in gALaxy cluStErs(2009)
- Subjects
Brightness ,Astronomy ,techniques ,Astrophysics ,Cosmology: observation ,01 natural sciences ,EWI-25428 ,law.invention ,law ,polarimetric [techniques] ,dark ages ,Faraday cage ,010303 astronomy & astrophysics ,Physics ,Line-of-sight ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,Astrophysics::Instrumentation and Methods for Astrophysics ,Polarization (waves) ,observations [cosmology] ,interferometric [techniques] ,radio continuum: ISM ,techniques: interferometric ,Brightness temperature ,ComputingMethodologies_DOCUMENTANDTEXTPROCESSING ,IR-93232 ,reionization ,Astrophysics - Instrumentation and Methods for Astrophysics ,techniques: polarimetric ,cosmology: observations ,diffuse radiation ,first stars ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,ISM [radio continuum] ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Radio telescope ,0103 physical sciences ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,Reionization ,Astrophysics::Galaxy Astrophysics ,010308 nuclear & particles physics ,Astronomy and Astrophysics ,METIS-309730 ,LOFAR ,Astronomy and Astrophysic ,Astrophysics - Astrophysics of Galaxies ,[SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM] ,Dark ages, reionization, first star ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,polarimetric - Abstract
This study aims to characterise the polarized foreground emission in the ELAIS-N1 field and to address its possible implications for the extraction of the cosmological 21-cm signal from the Low-Frequency Array - Epoch of Reionization (LOFAR-EoR) data. We use the high band antennas of LOFAR to image this region and RM-synthesis to unravel structures of polarized emission at high Galactic latitudes. The brightness temperature of the detected Galactic emission is on average 4 K in polarized intensity and covers the range from -10 to +13rad m^-2 in Faraday depth. The total polarized intensity and polarization angle show a wide range of morphological features. We have also used the Westerbork Synthesis Radio Telescope (WSRT) at 350 MHz to image the same region. The LOFAR and WSRT images show a similar complex morphology, at comparable brightness levels, but their spatial correlation is very low. The fractional polarization at 150 MHz, expressed as a percentage of the total intensity, amounts to 1.5%. There is no indication of diffuse emission in total intensity in the interferometric data, in line with results at higher frequencies. The wide frequency range, good angular resolution and good sensitivity make LOFAR an exquisite instrument for studying Galactic polarized emission at a resolution of 1-2 rad m^-2 in Faraday depth. The different polarised patterns observed at 150 MHz and 350 MHz are consistent with different source distributions along the line of sight wring in a variety of Faraday thin regions of emission. The presence of polarised foregrounds is a serious complication for Epoch of Reionization experiments. To avoid the leakage of polarized emission into total intensity, which can depend on frequency, we need to calibrate the instrumental polarization across the field of view to a small fraction of 1%., 12 pages, 9 figures, accepted for publication in A&A
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- 2014
21. LOFAR Low-band Antenna Observations of the 3C 295 and Boötes Fields: Source Counts and Ultra-steep Spectrum Sources
- Author
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Stappers, Benjamin, {van Weeren}, R J, {Williams}, W L, {Tasse}, C, {Röttgering}, H J A, {Rafferty}, D A, {van der Tol}, S, {Heald}, G, {White}, G J, {Shulevski}, A, {Best}, P, {Intema}, H T, {Bhatnagar}, S, {Reich}, W, {Steinmetz}, M, {van Velzen}, S, {En{\ss}lin}, T A, {Prandoni}, I, {de Gasperin}, F, {Jamrozy}, M, {Brunetti}, G, {Jarvis}, M J, {McKean}, J P, {Wise}, M W, {Ferrari}, C, {Harwood}, J, {Oonk}, J B R, {Hoeft}, M, {Kunert-Bajraszewska}, M, {Horellou}, C, {Wucknitz}, O, {Bonafede}, A, {Mohan}, N R, {Scaife}, A M M, {Klöckner}, H-R, {van Bemmel}, I M, {Merloni}, A, {Chyzy}, K T, {Engels}, D, {Falcke}, H, {Pandey-Pommier}, M, {Alexov}, A, {Anderson}, J, {Avruch}, I M, {Beck}, R, {Bell}, M E, {Bentum}, M J, {Bernardi}, G, {Breitling}, F, {Broderick}, J, {Brouw}, W N, {Brüggen}, M, {Butcher}, H R, {Ciardi}, B, {de Geus}, E, {de Vos}, M, {Deller}, A, {Duscha}, S, {Eislöffel}, J, {Fallows}, R A, {Frieswijk}, W, Garrett, Michael, {Grie{\ss}meier}, J, {Gunst}, A W, {Hamaker}, J P, {Hassall}, T E, {Hörandel}, J, {van der Horst}, A, {Iacobelli}, M, {Jackson}, N J, {Juette}, E, {Kondratiev}, V I, {Kuniyoshi}, M, {Maat}, P, {Mann}, G, {McKay-Bukowski}, D, {Mevius}, M, {Morganti}, R, {Munk}, H, {Offringa}, A R, {Orrù}, E, {Paas}, H, {Pandey}, V N, {Pietka}, G, {Pizzo}, R, {Polatidis}, A G, {Renting}, A, {Rowlinson}, A, {Schwarz}, D, {Serylak}, M, {Sluman}, J, {Smirnov}, O, {Stappers}, B W, {Stewart}, A, {Swinbank}, J, {Tagger}, M, {Tang}, Y, {Thoudam}, S, {Toribio}, C, {Vermeulen}, R, {Vocks}, C, {Zarka}, P, Astronomy, Netherlands Institute for Radio Astronomy (ASTRON), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], SKA South Africa, Ska South Africa, Rhodes University, Grahamstown, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Department of Astronomy and Astrophysics [PennState], Pennsylvania State University (Penn State), Penn State System-Penn State System, SLAC National Accelerator Laboratory (SLAC), Stanford University, University of Edinburgh, Department of Computer Science and Automation [Bangalore] (CSA), Indian Institute of Science [Bangalore] (IISc Bangalore), Max-Planck-Institut für Radioastronomie (MPIFR), Charles Darwin University, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Laboratoire Réactions et Génie des Procédés (LRGP), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Thüringer Landessternwarte Tautenburg (TLS), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Jacobs University [Bremen], School of Physics and Astronomy [Southampton], University of Southampton, Radboud university [Nijmegen], Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Leibniz-Institut für Astrophysik Potsdam (AIP), SRON Netherlands Institute for Space Research (SRON), Laboratoire de Chimie Physique Moléculaire (LCPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Medstar Research Institute, Institute of Mathematical and Physical Sciences, Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Dipartimento di Matematica 'Guido Castelnuovo' [Roma I] (Sapienza University of Rome), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome], Centre de Mathématiques Laurent Schwartz (CMLS), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Ruhr-Universität Bochum [Bochum], University of Oulu, Applied Stochastics (IMAPP), Oxford Astrophysics, University of Oxford [Oxford], Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, ANR-09-JCJC-0001,OPALES(2009), High Energy Astrophys. & Astropart. Phys (API, FNWI), Van Weeren, R.J., Williams, W.L., Tasse, C., Röttgering, H.J.A., Rafferty, D.A., Van Der Tol, S., Heald, G., White, G.J., Shulevski, A., Best, P., Intema, H.T., Bhatnagar, S., Reich, W., Steinmetz, M., Van Velzen, S., Enßlin, T.A., Prandoni, I., De Gasperin, F., Jamrozy, M., Brunetti, G., Jarvis, M.J., McKean, J.P., Wise, M.W., Ferrari, C., Harwood, J., Oonk, J.B.R., Hoeft, M., Kunert-Bajraszewska, M., Horellou, C., Wucknitz, O., Bonafede, A., Mohan, N.R., Scaife, A.M.M., Klöckner, H.-R., Van Bemmel, I.M., Merloni, A., Chyzy, K.T., Engels, D., Falcke, H., Pandey-Pommier, M., Alexov, A., Anderson, J., Avruch, I.M., Beck, R., Bell, M.E., Bentum, M.J., Bernardi, G., Breitling, F., Broderick, J., Brouw, W.N., Brüggen, M., Butcher, H.R., Ciardi, B., De Geus, E., De Vos, M., Deller, A., Duscha, S., Eislöffel, J., Fallows, R.A., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hamaker, J.P., Hassall, T.E., Hörandel, J., Van Der Horst, A., Iacobelli, M., Jackson, N.J., Juette, E., Kondratiev, V.I., Kuniyoshi, M., Maat, P., Mann, G., McKay-Bukowski, D., Mevius, M., Morganti, R., Munk, H., Offringa, A.R., Orrù, E., Paas, H., Pandey, V.N., Pietka, G., Pizzo, R., Polatidis, A.G., Renting, A., Rowlinson, A., Schwarz, D., Serylak, M., Sluman, J., Smirnov, O., Stappers, B.W., Stewart, A., Swinbank, J., Tagger, M., Tang, Y., Thoudam, S., Toribio, C., Vermeulen, R., Vocks, C., Zarka, P., Harvard University-Smithsonian Institution, Universiteit Leiden, Radboud University [Nijmegen], École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome] (UNIROMA), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), and University of Oxford
- Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,general, surveys [radio continuum] ,EWI-25425 ,Radio galaxy ,Astronomy ,techniques ,galaxies: active ,radio continuum: general ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,METIS-309728 ,surveys ,survey ,Source counts ,Astrophysics::Galaxy Astrophysics ,Physics ,Spectral index ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,Astronomy and Astrophysics ,BOOTES ,LOFAR ,Astronomy and Astrophysic ,Astrophysics - Astrophysics of Galaxies ,Redshift ,interferometric [techniques] ,IR-93230 ,Space and Planetary Science ,[SDU]Sciences of the Universe [physics] ,techniques: interferometric ,Astrophysics of Galaxies (astro-ph.GA) ,interferometric ,active [galaxies] ,ComputingMethodologies_DOCUMENTANDTEXTPROCESSING ,Spectral energy distribution ,general [radio continuum] ,Noise (radio) ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
We present LOFAR Low Band observations of the Bootes and 3C295 fields. Our images made at 34, 46, and 62 MHz reach noise levels of 12, 8, and 5 mJy beam$^{-1}$, making them the deepest images ever obtained in this frequency range. In total, we detect between 300 and 400 sources in each of these images, covering an area of 17 to 52 deg$^{2}$. From the observations we derive Euclidean-normalized differential source counts. The 62 MHz source counts agree with previous GMRT 153 MHz and VLA 74 MHz differential source counts, scaling with a spectral index of $-0.7$. We find that a spectral index scaling of $-0.5$ is required to match up the LOFAR 34 MHz source counts. This result is also in agreement with source counts from the 38 MHz 8C survey, indicating that the average spectral index of radio sources flattens towards lower frequencies. We also find evidence for spectral flattening using the individual flux measurements of sources between 34 and 1400 MHz and by calculating the spectral index averaged over the source population. To select ultra-steep spectrum ($\alpha < -1.1$) radio sources, that could be associated with massive high redshift radio galaxies, we compute spectral indices between 62 MHz, 153 MHz and 1.4 GHz for sources in the Bo\"otes field. We cross-correlate these radio sources with optical and infrared catalogues and fit the spectral energy distribution to obtain photometric redshifts. We find that most of these ultra-steep spectrum sources are located in the $ 0.7 \lesssim z \lesssim 2.5$ range., Comment: 26 pages, 20 figures, ApJ in press
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- 2014
22. Initial deep LOFAR observations of Epoch of Reionization windows: I. The North Celestial Pole
- Author
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M. A. Garrett, Vibor Jelić, Michel Tagger, B. Ciardi, Aris Karastergiou, Harish Vedantham, Marco Iacobelli, Michael W. Wise, Gianni Bernardi, Garrelt Mellema, F. Breitling, F. B. Abdalla, Panagiotis Labropoulos, H. Paas, R. J. van Weeren, Richard Fallows, Léon V. E. Koopmans, M. Kuniyoshi, Michiel A. Brentjens, W. N. Brouw, R. Nijboer, E. Juette, Emanuela Orru, Olaf Wucknitz, V. Veligatla, Gottfried Mann, Ben Stappers, John McKean, M. Mevius, A. G. Polatidis, J. M. Anderson, A. Alexov, Gerard H. Kuper, J. D. Mol, S. ter Veen, Annalisa Bonafede, R. Pizzo, A. W. Gunst, T. E. Hassall, M. Pandey-Pommier, Ph. Zarka, Joop Schaye, Geraint Harker, Michael Kramer, J. Sluman, P. Maat, Jason W. T. Hessels, M. J. Norden, H. J. A. Röttgering, A. R. Offringa, Philip Best, V. I. Kondratiev, Heino Falcke, V. N. Pandey, Chiara Ferrari, J. Noordam, S. Duscha, E. de Geus, John Conway, R. Vermeulen, Sarod Yatawatta, S. Kazemi, Matthias Hoeft, S. Daiboo, F. Batejat, Michael R. Bell, Wolfgang Reich, Saleem Zaroubi, J. M. Griessmeier, R. H. van de Brink, Rajat M. Thomas, Cyril Tasse, Y. Tang, J. W. Broderick, Emma Chapman, Mark J. Bentum, Stefan J. Wijnholds, J. van Leeuwen, Joel N. Bregman, H. Munk, Marcus Brüggen, F. de Gasperin, W. Frieswijk, I. M. Avruch, Oleg Smirnov, Matthias Steinmetz, Martin Bell, O. Martinez Rubi, de Antonius Bruyn, Netherlands Institute for Radio Astronomy (ASTRON), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Department of process and energy, Delft University of Technology (TU Delft), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Center for Astrophysics and Space Astronomy [Boulder] (CASA), University of Colorado [Boulder], Stockholm Observatory Department of Astronomy, Stockholm University, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Génétique Diversité et Ecophysiologie des Céréales (GDEC), Institut National de la Recherche Agronomique (INRA)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP), University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Onsala Space Observatory, Dept. of Radio and Space Science, Chalmers University of Technology, Chalmers University of Technology [Göteborg], Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Medstar Research Institute, Max-Planck-Institut für Radioastronomie (MPIFR), Radboud university [Nijmegen], Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Thüringer Landessternwarte Tautenburg (TLS), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford [Oxford], University of Amsterdam [Amsterdam] (UvA), Observatoire de Paris - Site de Meudon (OBSPM), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Center for Information Technology CIT, Université de Groningen, Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut National de la Recherche Agronomique (INRA), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Yatawatta, S., De Bruyn, A.G., Brentjens, M.A., Labropoulos, P., Pandey, V.N., Kazemi, S., Zaroubi, S., Koopmans, L.V.E., Offringa, A.R., Jelić, V., Martinez Rubi, O., Veligatla, V., Wijnholds, S.J., Brouw, W.N., Bernardi, G., Ciardi, B., Daiboo, S., Harker, G., Mellema, G., Schaye, J., Thomas, R., Vedantham, H., Chapman, E., Abdalla, F.B., Alexov, A., Anderson, J., Avruch, I.M., Batejat, F., Bell, M.E., Bell, M.R., Bentum, M., Best, P., Bonafede, A., Bregman, J., Breitling, F., Van De Brink, R.H., Broderick, J.W., Brüggen, M., Conway, J., De Gasperin, F., De Geus, E., Duscha, S., Falcke, H., Fallows, R.A., Ferrari, C., Frieswijk, W., Garrett, M.A., Griessmeier, J.M., Gunst, A.W., Hassall, T.E., Hessels, J.W.T., Hoeft, M., Iacobelli, M., Juette, E., Karastergiou, A., Kondratiev, V.I., Kramer, M., Kuniyoshi, M., Kuper, G., Van Leeuwen, J., Maat, P., Mann, G., McKean, J.P., Mevius, M., Mol, J.D., Munk, H., Nijboer, R., Noordam, J.E., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H.J.A., Sluman, J., Smirnov, O., Stappers, B., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Ter Veen, S., Vermeulen, R., Van Weeren, R.J., Wise, M., Wucknitz, O., Zarka, P., High Energy Astrophys. & Astropart. Phys (API, FNWI), Harvard University-Smithsonian Institution, Universiteit Leiden, Radboud University [Nijmegen], Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), and University of Oxford
- Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,Astronomy ,first stars ,FOS: Physical sciences ,Astrophysics::Cosmology and Extragalactic Astrophysics ,7. Clean energy ,01 natural sciences ,Instrumentation: interferometer ,METIS-302720 ,Celestial pole ,first stars -instrumentation: interferometers -techniques: interferometric -methods: data analysis ,0103 physical sciences ,dark ages ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,010303 astronomy & astrophysics ,Reionization ,Physics ,reionization ,instrumentation: interferometers ,techniques: interferometric ,methods: data analysis ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,010308 nuclear & particles physics ,IR-89500 ,Instrumentation: interferometers – Techniques: interferometric – Cosmology: observations ,Astrophysics::Instrumentation and Methods for Astrophysics ,EWI-24509 ,Astronomy and Astrophysics ,LOFAR ,Astronomy and Astrophysic ,Redshift ,Galaxy ,diffuse radiation ,Dark ages, reionization, first star ,Orders of magnitude (time) ,Space and Planetary Science ,Instrumentation: interferometers ,Techniques: interferometric ,ComputingMethodologies_DOCUMENTANDTEXTPROCESSING ,Ionosphere ,Astrophysics - Instrumentation and Methods for Astrophysics ,Noise (radio) ,Methods: data analysi ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
The aim of the LOFAR Epoch of Reionization (EoR) project is to detect the spectral fluctuations of the redshifted HI 21cm signal. This signal is weaker by several orders of magnitude than the astrophysical foreground signals and hence, in order to achieve this, very long integrations, accurate calibration for stations and ionosphere and reliable foreground removal are essential. One of the prospective observing windows for the LOFAR EoR project will be centered at the North Celestial Pole (NCP). We present results from observations of the NCP window using the LOFAR highband antenna (HBA) array in the frequency range 115 MHz to 163 MHz. The data were obtained in April 2011 during the commissioning phase of LOFAR. We used baselines up to about 30 km. With about 3 nights, of 6 hours each, effective integration we have achieved a noise level of about 100 microJy/PSF in the NCP window. Close to the NCP, the noise level increases to about 180 microJy/PSF, mainly due to additional contamination from unsubtracted nearby sources. We estimate that in our best night, we have reached a noise level only a factor of 1.4 above the thermal limit set by the noise from our Galaxy and the receivers. Our continuum images are several times deeper than have been achieved previously using the WSRT and GMRT arrays. We derive an analytical explanation for the excess noise that we believe to be mainly due to sources at large angular separation from the NCP., 19 pages, 24 figures. Draft version with low resolution images. Accepted on 08/01/2013 Astronomy & Astrophysics. Abstract abridged. Version with high resolution images: http://www.astro.rug.nl/~yatawatta/ncp_eor.pdf
- Published
- 2013
23. LOFAR: The LOw-Frequency ARray
- Author
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M. P. van Haarlem, M. W. Wise, A. W. Gunst, G. Heald, J. P. McKean, J. W. T. Hessels, A. G. de Bruyn, R. Nijboer, J. Swinbank, R. Fallows, M. Brentjens, A. Nelles, R. Beck, H. Falcke, R. Fender, J. Hörandel, L. V. E. Koopmans, G. Mann, G. Miley, H. Röttgering, B. W. Stappers, R. A. M. J. Wijers, S. Zaroubi, M. van den Akker, A. Alexov, J. Anderson, K. Anderson, A. van Ardenne, M. Arts, A. Asgekar, I. M. Avruch, F. Batejat, L. Bähren, M. E. Bell, M. R. Bell, I. van Bemmel, P. Bennema, M. J. Bentum, G. Bernardi, P. Best, L. Bîrzan, A. Bonafede, A.-J. Boonstra, R. Braun, J. Bregman, F. Breitling, R. H. van de Brink, J. Broderick, P. C. Broekema, W. N. Brouw, M. Brüggen, H. R. Butcher, W. van Cappellen, B. Ciardi, T. Coenen, J. Conway, A. Coolen, A. Corstanje, S. Damstra, O. Davies, A. T. Deller, R.-J. Dettmar, G. van Diepen, K. Dijkstra, P. Donker, A. Doorduin, J. Dromer, M. Drost, A. van Duin, J. Eislöffel, J. van Enst, C. Ferrari, W. Frieswijk, H. Gankema, M. A. Garrett, F. de Gasperin, M. Gerbers, E. de Geus, J.-M. Grießmeier, T. Grit, P. Gruppen, J. P. Hamaker, T. Hassall, M. Hoeft, H. A. Holties, A. Horneffer, A. van der Horst, A. van Houwelingen, A. Huijgen, M. Iacobelli, H. Intema, N. Jackson, V. Jelic, A. de Jong, E. Juette, D. Kant, A. Karastergiou, A. Koers, H. Kollen, V. I. Kondratiev, E. Kooistra, Y. Koopman, A. Koster, M. Kuniyoshi, M. Kramer, G. Kuper, P. Lambropoulos, C. Law, J. van Leeuwen, J. Lemaitre, M. Loose, P. Maat, G. Macario, S. Markoff, J. Masters, R. A. McFadden, D. McKay-Bukowski, H. Meijering, H. Meulman, M. Mevius, E. Middelberg, R. Millenaar, J. C. A. Miller-Jones, R. N. Mohan, J. D. Mol, J. Morawietz, R. Morganti, D. D. Mulcahy, E. Mulder, H. Munk, L. Nieuwenhuis, R. van Nieuwpoort, J. E. Noordam, M. Norden, A. Noutsos, A. R. Offringa, H. Olofsson, A. Omar, E. Orrú, R. Overeem, H. Paas, M. Pandey-Pommier, V. N. Pandey, R. Pizzo, A. Polatidis, D. Rafferty, S. Rawlings, W. Reich, J.-P. de Reijer, J. Reitsma, G. A. Renting, P. Riemers, E. Rol, J. W. Romein, J. Roosjen, M. Ruiter, A. Scaife, K. van der Schaaf, B. Scheers, P. Schellart, A. Schoenmakers, G. Schoonderbeek, M. Serylak, A. Shulevski, J. Sluman, O. Smirnov, C. Sobey, H. Spreeuw, M. Steinmetz, C. G. M. Sterks, H.-J. Stiepel, K. Stuurwold, M. Tagger, Y. Tang, C. Tasse, I. Thomas, S. Thoudam, M. C. Toribio, B. van der Tol, O. Usov, M. van Veelen, A.-J. van der Veen, S. ter Veen, J. P. W. Verbiest, R. Vermeulen, N. Vermaas, C. Vocks, C. Vogt, M. de Vos, E. van der Wal, R. van Weeren, H. Weggemans, P. Weltevrede, S. White, S. J. Wijnholds, T. Wilhelmsson, O. Wucknitz, S. Yatawatta, P. Zarka, A. Zensus, J. van Zwieten, Netherlands Institute for Radio Astronomy (ASTRON), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Institute of Mathematical and Physical Sciences, Radboud university [Nijmegen], Laboratoire de Chimie Physique Moléculaire (LCPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Max-Planck-Institut für Radioastronomie (MPIFR), University of Southampton, Leibniz-Institut für Astrophysik Potsdam (AIP), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Medical Center Haaglanden, SRON Netherlands Institute for Space Research (SRON), University of Edinburgh, Jacobs University [Bremen], Technische Universität Dresden = Dresden University of Technology (TU Dresden), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Department of Reproduction and Development, Erasmus University Rotterdam, London Institute for Mathematical Sciences, Netherlands Centre for Biodiversity, Leiden, The Netherlands, Thüringer Landessternwarte Tautenburg (TLS), Laboratoire Réactions et Génie des Procédés (LRGP), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Medstar Research Institute, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Plant Research International, Business Unit Bioscience, Wageningen University and Research [Wageningen] (WUR), Dipartimento di Matematica 'Guido Castelnuovo' [Roma I] (Sapienza University of Rome), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome], Centre de Mathématiques Laurent Schwartz (CMLS), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Peuplements végétaux et bioagresseurs en milieu tropical (UMR PVBMT), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Université de La Réunion (UR), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford [Oxford], Amsterdam Center for Multiscale Modeling, Vrije Universiteit Amsterdam [Amsterdam] (VU), Vrije Universiteit Medical Centre (VUMC), Queen's Medical Centre, National Radio Astronomy Observatory (NRAO), University of Oulu, Department of Economics, Bryant University, Center for Agricultural Research in Suriname CELOS and Department of Biology, Anton de Kom Universiteit van Suriname - Anton de Kom University of Suriname [Paramaribo] (UVS), DLR Institute of Aerospace Medicine, Deutsches Zentrum für Luft- und Raumfahrt [Köln] (DLR), Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Geophysical Institute [Bergen] (GFI / BiU), University of Bergen (UiB), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Department of Astronomy and Astrophysics [PennState], Pennsylvania State University (Penn State), Penn State System-Penn State System, Academic Medical Center - Academisch Medisch Centrum [Amsterdam] (AMC), School of Physics and Astronomy [Southampton], Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Rhodes University, Grahamstown, Center for Information Technology CIT, Université de Groningen, Processus d'Activation Sélective par Transfert d'Energie Uni-électronique ou Radiatif (UMR 8640) (PASTEUR), Université Pierre et Marie Curie - Paris 6 (UPMC)-Département de Chimie - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Center for Operations and Econometrics, Center of Operation Research and Econometrics [Louvain] (CORE), Université Catholique de Louvain = Catholic University of Louvain (UCL)-Université Catholique de Louvain = Catholic University of Louvain (UCL), Finca El Encin, Instituto Madrileño de Investigación y Desarrollo Rural, Agrario y Alimentario (IMIDRA), Department of Surgery (EINDHOVEN - Surgery), Catharina Hospital, Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Harvard-Smithsonian Center for Astrophysics (CfA), Smithsonian Institution-Harvard University [Cambridge], Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, ANR-09-JCJC-0001,OPALES(2009), Astronomy, KVI - Center for Advanced Radiation Technology, Radboud University [Nijmegen], Universiteit Leiden, Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome] (UNIROMA), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), University of Oxford, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Harvard University-Smithsonian Institution, UMR Peuplement Végétaux et Bioagresseurs en Milieu Tropical (UMR PVBMT - INRA), Institut National de la Recherche Agronomique (INRA), Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Technische Universität Dresden (TUD), university Rotterdam, PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Wageningen University and Research Centre [Wageningen] (WUR), Università degli Studi di Roma 'La Sapienza' [Rome], Department of Physics, University of Crete [Heraklion] (UOC), Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas (FORTH), Anton de Kom University of Suriname, Geophysical Institute [Bergen], University of Bergen (UIB), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, École normale supérieure - Paris (ENS Paris)-École normale supérieure - Paris (ENS Paris)-Centre National de la Recherche Scientifique (CNRS), SKA South Africa, Ska South Africa, Center for Operations and Econometrics, Universit´e catholique de Louvain and Fonds National de la Recherche Scientifique, Harvard University [Cambridge]-Smithsonian Institution, Observatoire de Paris - Site de Paris (OP), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), ANR-09-JCJC-0001,OPALES,nOn-thermal Processes in gALaxy cluStErs(2009), High Energy Astrophys. & Astropart. Phys (API, FNWI), Van Haarlem, M.P., Wise, M.W., Gunst, A.W., Heald, G., McKean, J.P., Hessels, J.W.T., De Bruyn, A.G., Nijboer, R., Swinbank, J., Fallows, R., Brentjens, M., Nelles, A., Beck, R., Falcke, H., Fender, R., Hörandel, J., Koopmans, L.V.E., Mann, G., Miley, G., Röttgering, H., Stappers, B.W., Wijers, R.A.M.J., Zaroubi, S., Van Den Akker, M., Alexov, A., Anderson, J., Anderson, K., Van Ardenne, A., Arts, M., Asgekar, A., Avruch, I.M., Batejat, F., Bähren, L., Bell, M.E., Bell, M.R., Van Bemmel, I., Bennema, P., Bentum, M.J., Bernardi, G., Best, P., Bîrzan, L., Bonafede, A., Boonstra, A.-J., Braun, R., Bregman, J., Breitling, F., Van De Brink, R.H., Broderick, J., Broekema, P.C., Brouw, W.N., Brüggen, M., Butcher, H.R., Van Cappellen, W., Ciardi, B., Coenen, T., Conway, J., Coolen, A., Corstanje, A., Damstra, S., Davies, O., Deller, A.T., Dettmar, R.-J., Van Diepen, G., Dijkstra, K., Donker, P., Doorduin, A., Dromer, J., Drost, M., Van Duin, A., Eislöffel, J., Van Enst, J., Ferrari, C., Frieswijk, W., Gankema, H., Garrett, M.A., De Gasperin, F., Gerbers, M., De Geus, E., Grießmeier, J.-M., Grit, T., Gruppen, P., Hamaker, J.P., Hassall, T., Hoeft, M., Holties, H.A., Horneffer, A., Van Der Horst, A., Van Houwelingen, A., Huijgen, A., Iacobelli, M., Intema, H., Jackson, N., Jelic, V., De Jong, A., Juette, E., Kant, D., Karastergiou, A., Koers, A., Kollen, H., Kondratiev, V.I., Kooistra, E., Koopman, Y., Koster, A., Kuniyoshi, M., Kramer, M., Kuper, G., Lambropoulos, P., Law, C., Van Leeuwen, J., Lemaitre, J., Loose, M., Maat, P., Macario, G., Markoff, S., Masters, J., McFadden, R.A., McKay-Bukowski, D., Meijering, H., Meulman, H., Mevius, M., Middelberg, E., Millenaar, R., Miller-Jones, J.C.A., Mohan, R.N., Mol, J.D., Morawietz, J., Morganti, R., Mulcahy, D.D., Mulder, E., Munk, H., Nieuwenhuis, L., Van Nieuwpoort, R., Noordam, J.E., Norden, M., Noutsos, A., Offringa, A.R., Olofsson, H., Omar, A., Orrú, E., Overeem, R., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A., Rafferty, D., Rawlings, S., Reich, W., De Reijer, J.-P., Reitsma, J., Renting, G.A., Riemers, P., Rol, E., Romein, J.W., Roosjen, J., Ruiter, M., Scaife, A., Van Der Schaaf, K., Scheers, B., Schellart, P., Schoenmakers, A., Schoonderbeek, G., Serylak, M., Shulevski, A., Sluman, J., Smirnov, O., Sobey, C., Spreeuw, H., Steinmetz, M., Sterks, C.G.M., Stiepel, H.-J., Stuurwold, K., Tagger, M., Tang, Y., Tasse, C., Thomas, I., Thoudam, S., Toribio, M.C., Van Der Tol, B., Usov, O., Van Veelen, M., Van Der Veen, A.-J., Ter Veen, S., Verbiest, J.P.W., Vermeulen, R., Vermaas, N., Vocks, C., Vogt, C., De Vos, M., Van Der Wal, E., Van Weeren, R., Weggemans, H., Weltevrede, P., White, S., Wijnholds, S.J., Wilhelmsson, T., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, A., and Van Zwieten, J.
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instrumentation: interferometers -radio continuum: general -radio lines: general -dark ages ,Computer science ,Astronomy ,INTERPLANETARY SCINTILLATION ,radio continuum: general ,7. Clean energy ,01 natural sciences ,Precision Array for Probing the Epoch of Reionization ,law.invention ,Observatory ,law ,first stars - telescopes ,dark ages ,instrumentation: interferometers ,010303 astronomy & astrophysics ,Telescope ,UNDERSTANDING RADIO POLARIMETRY ,Instrumentation: Interferometer ,SELF-CALIBRATION ,Interferometry ,ComputingMethodologies_DOCUMENTANDTEXTPROCESSING ,reionization ,Astrophysics - Instrumentation and Methods for Astrophysics ,radio lines: general ,first stars ,Z-GREATER-THAN-5.7 QUASARS ,FOS: Physical sciences ,Murchison Widefield Array ,0103 physical sciences ,RAY AIR-SHOWERS ,Angular resolution ,dark ages, reionization, first stars ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,Remote sensing ,010308 nuclear & particles physics ,telescopes ,Astronomy and Astrophysics ,LOFAR ,Astronomy and Astrophysic ,Sextant (astronomical) ,Dark ages, reionization, first star ,Space and Planetary Science ,[SDU]Sciences of the Universe [physics] ,PROBE WMAP OBSERVATIONS ,DIGITAL SKY SURVEY ,HIGH-REDSHIFT ,MONTE-CARLO SIMULATIONS ,INTERGALACTIC MEDIUM - Abstract
LOFAR, the LOw-Frequency ARray, is a new-generation radio interferometer constructed in the north of the Netherlands and across europe. Utilizing a novel phased-array design, LOFAR covers the largely unexplored low-frequency range from 10-240 MHz and provides a number of unique observing capabilities. Spreading out from a core located near the village of Exloo in the northeast of the Netherlands, a total of 40 LOFAR stations are nearing completion. A further five stations have been deployed throughout Germany, and one station has been built in each of France, Sweden, and the UK. Digital beam-forming techniques make the LOFAR system agile and allow for rapid repointing of the telescope as well as the potential for multiple simultaneous observations. With its dense core array and long interferometric baselines, LOFAR achieves unparalleled sensitivity and angular resolution in the low-frequency radio regime. The LOFAR facilities are jointly operated by the International LOFAR Telescope (ILT) foundation, as an observatory open to the global astronomical community. LOFAR is one of the first radio observatories to feature automated processing pipelines to deliver fully calibrated science products to its user community. LOFAR's new capabilities, techniques and modus operandi make it an important pathfinder for the Square Kilometre Array (SKA). We give an overview of the LOFAR instrument, its major hardware and software components, and the core science objectives that have driven its design. In addition, we present a selection of new results from the commissioning phase of this new radio observatory., Comment: 56 pages, 34 figures, accepted for publication by A&A
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24. The LOFAR radio environment
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R.-J. Dettmar, Steve Rawlings, Vibor Jelić, Benedetta Ciardi, Ben Stappers, Aris Karastergiou, Y. Tang, R. Pizzo, V. N. Pandey, A. Alexov, Michael W. Wise, Gianni Bernardi, J. Eisloeffel, J. Sluman, W. A. van Cappellen, Panagiotis Labropoulos, Garrelt Mellema, A. Schoenmakers, M. Mevius, John Conway, P. Maat, M. P. van Haarlem, Rainer Beck, G. van Diepen, M. J. Norden, Heino Falcke, A. W. Gunst, Sarod Yatawatta, R. Nijboer, V. Veligatla, Joop Schaye, J. M. Anderson, D. A. Rafferty, S. Daiboo, M. Kuniyoshi, Michael R. Bell, A. G. Polatidis, A. van Duin, H. Paas, Harish Vedantham, A. G. de Bruyn, V. I. Kondratiev, H. Meulman, A. van Ardenne, Harvey Butcher, J. D. Mol, Laura Birzan, M. Pandey, Michel Tagger, Michiel A. Brentjens, M. Gerbers, Jason W. T. Hessels, George Heald, Matthias Steinmetz, Rob Fender, Marcus Brüggen, Annalisa Bonafede, Gottfried Mann, Mark J. Bentum, Saleem Zaroubi, J. Noordam, Charlotte Sobey, John McKean, John D. Swinbank, Olaf Wucknitz, Gerard H. Kuper, Stefan J. Wijnholds, O. Martinez-Ruby, Léon V. E. Koopmans, Ph. Zarka, Philip Best, Ashish Asgekar, Y. Koopman, R. Vermeulen, A. R. Offringa, R. J. van Weeren, Matthias Hoeft, A. Horneffer, Huub Röttgering, M. Avruch, T. E. Hassall, Martin Bell, J. M. Griessmeier, Geraint Harker, M. de Vos, Ralph A. M. J. Wijers, Christian Vocks, W. Frieswijk, Wolfgang Reich, Oleg Smirnov, Cyril Tasse, J. W. Broderick, F. Breitling, S. Kazemi, J. van Leeuwen, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Netherlands Institute for Radio Astronomy (ASTRON), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Department of process and energy, Delft University of Technology (TU Delft), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Observatoire de Paris, Université Paris sciences et lettres (PSL), Laboratoire de Chimie Physique Moléculaire (LCPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), University of Southampton, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], Max-Planck-Institut für Radioastronomie (MPIFR), Radboud university [Nijmegen], Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], University of Amsterdam [Amsterdam] (UvA), Thüringer Landessternwarte Tautenburg (TLS), Oxford Astrophysics, University of Oxford [Oxford], Center for Agricultural Research in Suriname CELOS and Department of Biology, Anton de Kom Universiteit van Suriname - Anton de Kom University of Suriname [Paramaribo] (UVS), Center for Information Technology CIT, Université de Groningen, Department of Astronomy and Astrophysics [PennState], Pennsylvania State University (Penn State), Penn State System-Penn State System, Rhodes University, Grahamstown, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), Department of Reproduction and Development, Erasmus University Rotterdam, Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Offringa, A.R., De Bruyn, A.G., Zaroubi, S., Van Diepen, G., Martinez-Ruby, O., Labropoulos, P., Brentjens, M.A., Ciardi, B., Daiboo, S., Harker, G., Jelić, V., Kazemi, S., Koopmans, L.V.E., Mellema, G., Pandey, V.N., Pizzo, R.F., Schaye, J., Vedantham, H., Veligatla, V., Wijnholds, S.J., Yatawatta, S., Zarka, P., Alexov, A., Anderson, J., Asgekar, A., Avruch, M., Beck, R., Bell, M., Bell, M.R., Bentum, M., Bernardi, G., Best, P., Birzan, L., Bonafede, A., Breitling, F., Broderick, J.W., Brüggen, M., Butcher, H., Conway, J., De Vos, M., Dettmar, R.J., Eisloeffel, J., Falcke, H., Fender, R., Frieswijk, W., Gerbers, M., Griessmeier, J.M., Gunst, A.W., Hassall, T.E., Heald, G., Hessels, J., Hoeft, M., Horneffer, A., Karastergiou, A., Kondratiev, V., Koopman, Y., Kuniyoshi, M., Kuper, G., Maat, P., Mann, G., McKean, J., Meulman, H., Mevius, M., Mol, J.D., Nijboer, R., Noordam, J., Norden, M., Paas, H., Pandey, M., Pizzo, R., Polatidis, A., Rafferty, D., Rawlings, S., Reich, W., Röttgering, H.J.A., Schoenmakers, A.P., Sluman, J., Smirnov, O., Sobey, C., Stappers, B., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Van Ardenne, A., Van Cappellen, W., Van Duin, A.P., Van Haarlem, M., Van Leeuwen, J., Van Weeren, R.J., Vermeulen, R., Vocks, C., Wijers, R.A.M.J., Wise, M., Wucknitz, O., UMR Peuplement Végétaux et Bioagresseurs en Milieu Tropical (UMR PVBMT - INRA), Institut National de la Recherche Agronomique (INRA), Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Anton de Kom University of Suriname, Rhodes University, SKA South Africa, Ska South Africa, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), university Rotterdam, Astronomy, Kapteyn Astronomical Institute, Peuplements végétaux et bioagresseurs en milieu tropical (UMR PVBMT), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Université de La Réunion (UR), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), and High Energy Astrophys. & Astropart. Phys (API, FNWI)
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Astronomy ,instrumentation: interferometers ,methods: data analysis ,techniques: interferometric ,telescopes ,radio continuum: general ,FOS: Physical sciences ,RFI ,02 engineering and technology ,Interference (wave propagation) ,01 natural sciences ,EWI-22636 ,Instrumentation: interferometer ,Radio continuum: general ,REMOVAL ,Instrumentation: interferometers - Methods: data analysis - Techniques: interferometric - Telescopes - Radio continuum: general ,0103 physical sciences ,Broadband ,0202 electrical engineering, electronic engineering, information engineering ,Range (statistics) ,010303 astronomy & astrophysics ,IR-82457 ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,Telescope ,FILTERING TECHNIQUES ,Remote sensing ,Significant difference ,INTERFERENCE MITIGATION ,Linearity ,ASTRONOMY ,020206 networking & telecommunications ,Astronomy and Astrophysics ,Time resolution ,LOFAR ,Astronomy and Astrophysic ,Space and Planetary Science ,[SDU]Sciences of the Universe [physics] ,Techniques: interferometric ,TELESCOPES ,ComputingMethodologies_DOCUMENTANDTEXTPROCESSING ,Environmental science ,Astrophysics - Instrumentation and Methods for Astrophysics ,METIS-293223 ,Radio astronomy ,Methods: data analysi - Abstract
Aims: This paper discusses the spectral occupancy for performing radio astronomy with the Low-Frequency Array (LOFAR), with a focus on imaging observations. Methods: We have analysed the radio-frequency interference (RFI) situation in two 24-h surveys with Dutch LOFAR stations, covering 30-78 MHz with low-band antennas and 115-163 MHz with high-band antennas. This is a subset of the full frequency range of LOFAR. The surveys have been observed with a 0.76 kHz / 1 s resolution. Results: We measured the RFI occupancy in the low and high frequency sets to be 1.8% and 3.2% respectively. These values are found to be representative values for the LOFAR radio environment. Between day and night, there is no significant difference in the radio environment. We find that lowering the current observational time and frequency resolutions of LOFAR results in a slight loss of flagging accuracy. At LOFAR's nominal resolution of 0.76 kHz and 1 s, the false-positives rate is about 0.5%. This rate increases approximately linearly when decreasing the data frequency resolution. Conclusions: Currently, by using an automated RFI detection strategy, the LOFAR radio environment poses no perceivable problems for sensitive observing. It remains to be seen if this is still true for very deep observations that integrate over tens of nights, but the situation looks promising. Reasons for the low impact of RFI are the high spectral and time resolution of LOFAR; accurate detection methods; strong filters and high receiver linearity; and the proximity of the antennas to the ground. We discuss some strategies that can be used once low-level RFI starts to become apparent. It is important that the frequency range of LOFAR remains free of broadband interference, such as DAB stations and windmills., Comment: Accepted for publication in A&A. 15 figures, 16 pages
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- 2013
25. First LOFAR observations at very low frequencies of cluster-scale non-thermal emission: the case of Abell 2256
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R. J. van Weeren, H. J. A. Röttgering, D. A. Rafferty, R. Pizzo, A. Bonafede, M. Brüggen, G. Brunetti, C. Ferrari, E. Orrù, G. Heald, J. P. McKean, C. Tasse, F. de Gasperin, L. Bîrzan, J. E. van Zwieten, S. van der Tol, A. Shulevski, N. Jackson, A. R. Offringa, J. Conway, H. T. Intema, T. E. Clarke, I. van Bemmel, G. K. Miley, G. J. White, M. Hoeft, R. Cassano, G. Macario, R. Morganti, M. W. Wise, C. Horellou, E. A. Valentijn, O. Wucknitz, K. Kuijken, T. A. Enßlin, J. Anderson, A. Asgekar, I. M. Avruch, R. Beck, M. E. Bell, M. R. Bell, M. J. Bentum, G. Bernardi, P. Best, A.-J. Boonstra, M. Brentjens, R. H. van de Brink, J. Broderick, W. N. Brouw, H. R. Butcher, W. van Cappellen, B. Ciardi, J. Eislöffel, H. Falcke, R. Fender, M. A. Garrett, M. Gerbers, A. Gunst, M. P. van Haarlem, J. P. Hamaker, T. Hassall, J. W. T. Hessels, L. V. E. Koopmans, G. Kuper, J. van Leeuwen, P. Maat, R. Millenaar, H. Munk, R. Nijboer, J. E. Noordam, V. N. Pandey, M. Pandey-Pommier, A. Polatidis, W. Reich, A. M. M. Scaife, A. Schoenmakers, J. Sluman, B. W. Stappers, M. Steinmetz, J. Swinbank, M. Tagger, Y. Tang, R. Vermeulen, M. de Vos, Astronomy, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), ANR-09-JCJC-0001,OPALES(2009), European Project: 224897,EC:FP7:PEOPLE,FP7-PEOPLE-2007-2-2-ERG,WIDEMAP(2008), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Van Weeren, R.J., Röttgering, H.J.A., Rafferty, D.A., Pizzo, R., Bonafede, A., Brüggen, M., Brunetti, G., Ferrari, C., Orrù, E., Heald, G., McKean, J.P., Tasse, C., De Gasperin, F., Bîrzan, L., Van Zwieten, J.E., Van Der Tol, S., Shulevski, A., Jackson, N., Offringa, A.R., Conway, J., Intema, H.T., Clarke, T.E., Van Bemmel, I., Miley, G.K., White, G.J., Hoeft, M., Cassano, R., MacArio, G., Morganti, R., Wise, M.W., Horellou, C., Valentijn, E.A., Wucknitz, O., Kuijken, K., Enßlin, T.A., Anderson, J., Asgekar, A., Avruch, I.M., Beck, R., Bell, M.E., Bell, M.R., Bentum, M.J., Bernardi, G., Best, P., Boonstra, A.-J., Brentjens, M., Van De Brink, R.H., Broderick, J., Brouw, W.N., Butcher, H.R., Van Cappellen, W., Ciardi, B., Eislöffel, J., Falcke, H., Fender, R., Garrett, M.A., Gerbers, M., Gunst, A., Van Haarlem, M.P., Hamaker, J.P., Hassall, T., Hessels, J.W.T., Koopmans, L.V.E., Kuper, G., Van Leeuwen, J., Maat, P., Millenaar, R., Munk, H., Nijboer, R., Noordam, J.E., Pandey, V.N., Pandey-Pommier, M., Polatidis, A., Reich, W., Scaife, A.M.M., Schoenmakers, A., Sluman, J., Stappers, B.W., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Vermeulen, R., De Vos, M., and High Energy Astrophys. & Astropart. Phys (API, FNWI)
- Subjects
galaxies: clusters: individual: Abell 2256 ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,PARTICLE-ACCELERATION ,COMA CLUSTER ,Astronomy ,Astrophysics::High Energy Astrophysical Phenomena ,ASTROPHYSICAL SHOCKS ,radio continuum: general ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Radio spectrum ,MAGNETIC-FIELDS ,Relativistic particle ,X-RAY-EMISSION ,METIS-293218 ,0103 physical sciences ,MERGING GALAXY CLUSTER ,EXTENDED RADIO-EMISSION ,Telescope ,010303 astronomy & astrophysics ,Galaxy cluster ,Astrophysics::Galaxy Astrophysics ,Physics ,[PHYS]Physics [physics] ,Spectral index ,010308 nuclear & particles physics ,Astronomy and Astrophysics ,telescopes ,LOFAR ,Astronomy and Astrophysic ,EWI-22624 ,Galaxy ,SHOCK ACCELERATION ,DEEP 1.4 GHZ ,Radio halo ,Space and Planetary Science ,ComputingMethodologies_DOCUMENTANDTEXTPROCESSING ,Halo ,large-scale structure of Universe ,IR-82401 ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,SKY SURVEY ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
Abell 2256 is one of the best known examples of a galaxy cluster hosting large-scale diffuse radio emission that is unrelated to individual galaxies. It contains both a giant radio halo and a relic, as well as a number of head-tail sources and smaller diffuse steep-spectrum radio sources. The origin of radio halos and relics is still being debated, but over the last years it has become clear that the presence of these radio sources is closely related to galaxy cluster merger events. Here we present the results from the first LOFAR Low band antenna (LBA) observations of Abell 2256 between 18 and 67 MHz. To our knowledge, the image presented in this paper at 63 MHz is the deepest ever obtained at frequencies below 100 MHz in general. Both the radio halo and the giant relic are detected in the image at 63 MHz, and the diffuse radio emission remains visible at frequencies as low as 20 MHz. The observations confirm the presence of a previously claimed ultra-steep spectrum source to the west of the cluster center with a spectral index of -2.3 \pm 0.4 between 63 and 153 MHz. The steep spectrum suggests that this source is an old part of a head-tail radio source in the cluster. For the radio relic we find an integrated spectral index of -0.81 \pm 0.03, after removing the flux contribution from the other sources. This is relatively flat which could indicate that the efficiency of particle acceleration at the shock substantially changed in the last \sim 0.1 Gyr due to an increase of the shock Mach number. In an alternative scenario, particles are re-accelerated by some mechanism in the downstream region of the shock, resulting in the relatively flat integrated radio spectrum. In the radio halo region we find indications of low-frequency spectral steepening which may suggest that relativistic particles are accelerated in a rather inhomogeneous turbulent region., Comment: 13 pages, 13 figures, accepted for publication in A\&A on April 12, 2012
- Published
- 2012
26. LOFAR: Recent Imaging Results and Future Prospects
- Author
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Carlos Sotomayor, John Conway, Giulia Macario, David Rafferty, Rainer Beck, Huub Röttgering, Joris E. van Zwieten, Roberto Pizzo, Emanuela Orrú, Cyril Tasse, Francesco de Gasperin, Chiara Ferrari, Annalisa Bonafede, Sebastiaan van der Tol, Reinout J. van Weeren, A. Horneffer, A. R. Offringa, John McKean, Marijke Haverkorn, James M. Anderson, Laura Birzan, Anna M. M. Scaife, Neal Jackson, Olaf Wucknitz, H. Miraghaei, Michael R. Bell, Monica Trasatti, Ilse van Bemmel, George Heald, Aleksandar Shulevski, Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides (CASSIOPEE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Heald, George, Bell, Michael R., Horneffer, Andrea, Offringa, A.R., Pizzo, Roberto, van der Tol, Sebastiaan, van Weeren, Reinout J., van Zwieten, Joris E., Anderson, James M., Beck, Rainer, van Bemmel, Ilse, Bîrzan, Laura, Bonafede, Annalisa, Conway, John, Ferrari, Chiara, De Gasperin, Francesco, Haverkorn, Marijke, Jackson, Neal, Macario, Giulia, McKean, John, Miraghaei, Halime, Orrù, Emanuela, Rafferty, David, Röttgering, Huub, Scaife, Anna, Shulevski, Aleksandar, Sotomayor, Carlo, Tasse, Cyril, Trasatti, Monica, Wucknitz, Olaf, and Kapteyn Astronomical Institute
- Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,Astronomy ,FOS: Physical sciences ,Image processing ,02 engineering and technology ,Astrophysics ,01 natural sciences ,law.invention ,Telescope ,Radio continuum: general ,Software ,law ,020204 information systems ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,010303 astronomy & astrophysics ,ComputingMilieux_MISCELLANEOUS ,CALIBRATION ,Physics ,RADIO ,business.industry ,Astronomy and Astrophysics ,LOFAR ,Astronomy and Astrophysic ,Instrumentation: interferometers ,Space and Planetary Science ,Systems engineering ,Instrumentation: interferometers - Radio continuum: general ,business ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
The Low Frequency Array (LOFAR) is under construction in the Netherlands and in several surrounding European countries. In this contribution, we describe the layout and design of the telescope, with a particular emphasis on the imaging characteristics of the array when used in its "standard imaging" mode. After briefly reviewing the calibration and imaging software used for LOFAR image processing, we show some recent results from the ongoing imaging commissioning efforts. We conclude by summarizing future prospects for the use of LOFAR in observing the little-explored low frequency Universe., Accepted for publication in special issue of Journal of Astrophysics and Astronomy: conference proceedings of "Diffuse Relativistic Plasmas" conference, Bangalore, 1-4 March 2011
- Published
- 2011
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